甲状腺破壊ラットにおける小脳発達の病理組織学および定量組織学的研究

Abstract

Sprague-Dawley white rats were used for this study. New-born male rats were each radiothyroidectomized by intraperitoneal injection of 100μCi of131I. The animals were perfused on days 7,15,20,34 and 96 with paraformaldehyde-glutaraldehyde mixture. Cerebellums were removed and chopped sagittally on the midline. The tissues, from cerebellar cortex in the pyramis, embedded in low viscosity epoxy resin. Before thinsectioning, tissue was trimed in the molecular layer. Tissue was ultra-thinsectioned on the ultramicrotome, stained with ulanyl acetate and lead nitrate, and viewed with electron microscope. On the other hand, cerebellum embedded in paraffin, was thinsectioned on the microtome, stained with Hematoxylin-Eosin, Kluver-Barrera and Bodian stain, and observed with light microscope. On light microscopic view, external granular layer remained at 20 days in hypothyroidal animals. But, in normal control rats on the same day, external granular layer already disappeared. The width of the molecular layer of the cerbellar cortex in the pyramis was measured; at 15 days, the data in control was significantly larger than in hypothroid rats, at the other days, not significant in the comparison between hypothyroid rats and normal control. On electron microscopic observation, there was no abnormal structure and no qualitative change in the molecular layer of the cerebellar cortex in both groups. But there was quantitative difference between them. Number of synaptogenesis between parallel fiber and Purkinjedendritic spine in hypothyroid rats was less than in normal control. Morphometric study was tried with computerized digitizer on the electron microscopic photograph in the molecular layer at 35560 magnification, as follows;(1) Counts of synaptic profiles p er unit area.(2) Length of post-synaptic thickening.(3) Area of Purkinje-dendritic spine. Samples for these morphometric items were selected from outer and inner halves of the molecular layer in cerebellum.10 samples were taken from each zone. These were measured from the magnified positives, printed on the quarters at 35560 magnification. Gray type I synapses between parallel fiber terminals and Purkinje-dendritic spines were selected and measured for these three items on each photographs. Several statistical comparison between hypothyroid and control groups were made. As the result, there were many significant differences in the counts of synaptic profiles. For length of post-synaptic thickening and area of Purkinje-dendritic spine, there were some significant differences in comparison between each days, and between inner half and outer half within each groups. On these statistical significant differences, developmental disturbance of the cerebellar cortex in the neonatal hypothyroid rats was clarified.